Method for operating a gas turbo group
A gas turbo group has a combustion chamber comprising a catalytic burner stage (2), a preburner stage (1) located upstream from the catalytic burner stage, as well as a non-catalytic burner stage (11, 5, 6) located downstream from the catalytic burner stage. The preburner stage serves to always maintain a temperature (T1) at the inlet into the catalytic stage that corresponds at least to a minimum temperature (TMIN) necessary for operating the catalytic burner stage. According to the invention, the gas turbo group is operated so that the burner stage located downstream from the catalytic combustion chamber is taken into operation only when the temperature (T2) at the outlet from the catalytic stage has reached an upper limit in the presence of a maximum combustion air mass flow.
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This application claims priority under 35 U.S.C. § 119 to Swiss patent application number 2003 0199/03, filed 11 Feb. 2003, by Jaan Hellat et al., the entirety of which is incorporated by reference herein.
1. Technical Field of Application
The present invention relates to a method for operating a gas turbo group.
2. State of the Art
The catalytic conversion of fuels presents an opportunity for generating heat with few noxious substances. However, a disadvantage in using gas turbo groups is the limitation of achievable temperatures, which is necessary in particular because of life span considerations. The turbine inlet temperatures that are desirable today in the interest of good efficiencies and high unit performance cannot be achieved with catalytic combustion chambers alone: While the combustion chambers of modern gas turbines generate hot gas temperatures of, for example, about 1450° C., a catalytic combustion chamber can only be operated up to temperatures of approximately 1000° C.
EP 694 740 describes the arrangement of a self-igniting combustion chamber, of the type also known from EP 669 500, downstream from a catalytic stage. The maximum outlet temperature of the catalyzer of approximately 1000° C.—EP 694 740 specifies 800° C. to 1100° C.—is optimally suitable for the minimum temperature required for the stable and safe function of a self-igniting combustion chamber, which, depending on the specific fuel, is, for example 900–950° C. Because of the relatively low thermal load—the temperature differential to be overcome is generally less than 600° C.—of the operation with good premixing of fuel and combustion gas, as well as a very low-fuel combustion, which again is associated with very few problems because of the high inlet temperature, such self-igniting combustion chambers have a very low nitrogen oxide emission and good burn-out. EP 694 740 specifies to use a vortex generator of a premix burner known from EP 321 809 to prepare the fuel-air mixture for the catalyzer, but emphasizes that no flame stabilization may take place there.
EP 767 345 discloses a gas turbo group with a multi-stage burner system consisting of a catalytic first burner stage, a non-catalytic second burner stage, as well as an interposed start-up burner. A separate preparation of the fuel-air mixture is provided for the catalytic burner stage in order to enable an optimization of this mixture. The mixture supplied to the catalytic burner stage is preheated by a thermal reactor with a heat source that is not further specified. The catalytic burner stage works at outlet temperatures of approximately 950° C., so that self-igniting burners, as known from EP 694 740 or EP 669 500, can be used in the second burner stage. The burner system proposed in this publication is supposed to prevent that the catalytic burner stage is supplied with hot gases or waste gases from a preceding combustion. When starting up a gas turbo group, it is first driven up to approximately 20% of its relative power with the start-up burner, before the catalytic burner stage is taken into operation. Then the second burner stage, which works downstream from the start-up burner, is added. The preparation of the fuel-air mixture for the catalytic burner stage used in this publication is, however, very complicated and expensive. In addition, under a full load, the preparation stage should be shut down, which means that it is not possible to react adequately to rapid load changes. The start-up burner also only operates up to approximately 20% of the relative power of the gas turbo group. Since a spontaneous and quick switching in of the start-up burner is required, the power reduction from a high load to below 20% of relative power is also critical here. Especially in the presence of highly transient operating states, such as a load rejection, where the power is abruptly reduced to or near zero by opening the generator or power switch of a stationary gas turbo group used for power generation, or during protective load shedding, where the power is reduced with a very high gradient of, for example, approximately 50% per minute, a timely interception of the thermal power can no longer be reliably ensured with a preburner that will be operated when a standstill occurs. Intermittent operation of the catalytic stage also causes undesired and even damaging thermal shocks to the frequently ceramic carrier material of the catalyzer.
The lowest emission values are achieved if the smallest possible portion of the thermal power conversion is accomplished by non-catalytic combustion.
DESCRIPTION OF THE INVENTIONIt is the objective of the invention to disclose a method of the aforementioned type that avoids the disadvantages of the state of the art. In particular, the objective is to specify an operating concept for a gas turbo group with a combustion chamber having a catalytic stage in such a way that the favorable emission behavior of the catalytic stage will be effective over the largest possible power range.
This objective is realized with the method according to Claim 1. Advantageous designs of the method are the subject matter of the secondary claims or can be found in the following specification and exemplary embodiments.
The core of the invention therefore consists of varying the combustion air mass flow in a gas turbo group having a catalytic stage and a following, non-catalytic stage in such a way that, with a variable fuel mass flow, the temperature at the outlet of the catalytic stage remains as constant as possible, and only then feeding additional fuel to the burner stages and/or combustion chambers located downstream from the catalytic stage when the combustion air mass flow is at a maximum.
In one embodiment of the invention, the combustion air mass flow is changed by adjusting an adjustable compressor guide row, in particular an adjustable pre-guide row of the compressor. It is known, for example, to adjust an adjustable pre-guide row of a compressor between a maximum closed position with a smallest mass flow and a completely open position with a maximum mass flow, whereby the compressor mass flow correlates very well with the combustion air mass flow.
According to another embodiment of the invention, the combustion air mass flow is increased by cooling the suction air upstream from the compressor, and conversely is reduced by reducing the cooling power applied for cooling.
Naturally, both methods can be combined and, preferably, cascaded. In a preferred embodiment, given a rising fuel mass flow, first the pre-guide row is opened in order to limit the temperature at the compressor outlet. Once this pre-guide row has been completely opened, the cooling power for the suction air, in the presence of a rising fuel mass flow, is increased upstream from the compressor in such a way that the temperature remains constant at the outlet from the catalytic stage, even though the fuel mass flow rises towards the catalytic stage.
In a preferred embodiment of the invention, the pre-guide row is kept in the maximum closed position as long as the temperature at the catalyzer outlet has not reached the set value or upper limit; to increase the power, only the total fuel mass flow is increased then, and no fuel is supplied to the combustion chambers or burner stages located downstream from the catalytic burner stage.
Completely analogously, all other measures for increasing the combustion air mass flow, especially for cooling the combustion air mass flow, are preferably deactivated until a set temperature value, which advantageously corresponds in essence to the maximum permanently permissible temperature of the catalyst material, is reached at the outlet of the catalytic combustion stage.
If this set temperature value is reached in the presence of a rising fuel mass flow, the measures for increasing the combustion air mass flow are activated. Naturally, the temperature at the outlet from the catalytic stage decreases with a constant fuel mass flow and elevated combustion air mass flow. As described, the increase of the combustion air mass flow is preferably brought about by adjusting an adjustable guide row of the compressor accordingly, in particular by opening an adjustable pre-guide row and/or by increasing the mass flow-specific cooling power for measures for cooling the suction air. Conversely, the temperature at the outlet from the catalytic stage rises when the combustion air mass flow decreases. As described, the reduction of the combustion air mass flow is preferably brought about by adjusting an adjustable guide row of the compressor accordingly, in particular by partially closing an adjustable pre-guide row and/or by decreasing the mass flow-specific cooling power for measures for cooling the suction air. In this way, the temperature at the catalyzer outlet can be regulated to the desired value. Once the combustion air mass flow has been maximized, yet another increase in the total fuel mass flow is necessary in order to achieve a set effective power of the gas turbo group, the fuel mass flow metered to the catalytic stage is adjusted so that the temperature at the catalyzer outlet remains at the desired value, and a second partial fuel mass flow is supplied to burners or burner stages, for example, a following non-catalytic stage, located downstream from the catalytic stage, and is converted there. According to the invention, the total fuel mass flow is distributed so that always the greatest possible portion is converted in the catalytic stage, in general by always keeping the temperature at the catalyzer outlet essentially at the upper permanently permissible limit. The invention is based on the concept, if it is no longer possible to do so otherwise when power is increased, of supplying fuel to a non-catalytic stage located downstream from the catalytic stage.
The gas turbo group according to the invention furthermore ensures operation with especially few noxious substances in particular when a non-catalytic stage following the catalytic stage works according to the principle of a self-igniting combustion chamber, since then a very lean premixed fuel-air mixture can be converted. Such a combustion chamber is known from EP 674 740. The catalytic burner stage as well as the quantity of fuel supplied to this burner stage are designed, for example, for an outlet temperature of approximately 900° C. to 950° C. or higher, whereby the permanently permissible temperature that ultimately represents the limiting factor naturally must be complied with.
The operation according to the invention of a gas turbo group with a combustion chamber known, for example, from EP 674 740, enables a low-emissions partial load operation, since the highest possible power range of the gas turbo group is provided by the catalytic burner stage. There may be a disadvantageous tendency with this type of operation that the waste gas temperature of the gas turbo group is very low over a wide power range in the partial load range. In combination operation, with a following waste heat steam generator whose steam is supplied to a steam turbo group, live steam data that permit a problem-free, unrestricted operation of the water-steam cycle, are therefore only generated at a high load. To use waste heat, the use of a closed gas turbine in the low temperature cycle, as proposed in WO 03/076781, is therefore possible for the operation according to the invention of the gas turbo group. The relevant disclosed content of WO 03/076781 thus represents an integral part of this publication.
During a load rejection, a preferred and advantageous embodiment of the method according to the invention provides that at first the second, non-catalytic burner stage is directly shut off, so that the compressor outlet temperature falls to idle level. The compressor pre-guide row remains standing open for several seconds. At the same time, or immediately after the second burner stage is shut off, the fuel mass flow supplied to the preburner is greatly increased, and the preburner stage is preferably operated with a predetermined, high fuel mass flow, in order to prevent the extinction of the catalyst of the catalytic burner stage; after this, the fuel quantity of the preburner stage can be adjusted to the fuel quantity necessary in idle operation of the gas turbo group. The fuel quantity supplied to the catalytic burner stage is hereby regulated in such a way that the rotor speed of the gas turbine is restricted to the nominal speed. During a subsequent load increase, the second burner stage is then again taken into operation again in order to regulate the load.
The invention is explained in more detail below in reference to exemplary embodiments illustrated in the drawing. In the drawing:
Such a quick drop in power occurs with a load rejection.
- 1 preburner, preburner stage
- 2 catalytic burner stage
- 3 low pressure combustion chamber, self-igniting combustion chamber, non-catalytic burner stage
- 4 turbine
- 5 fuel lance
- 6 combustion chamber of self-igniting combustion chamber
- 11 vortex generator
- 12 compressor
- 13 generator
- 14 mixing section
- 15 shaft
- 16 regulating element
- 17 regulating element
- 18 regulating element
- 21 ambient air
- 22 condensed air
- 23 combustion air
- 24 compressed flue gas
- 25 relaxed flue gas, waste gas
- 26 air stream of preburner
- 31 regulator
- 32 regulator
- 33 regulator
- 35 regulator
- 121 adjustable pre-guide row
- {dot over (m)}FUEL total fuel mass flow
- {dot over (m)}C fuel mass flow to catalytic burner stage
- {dot over (m)}P fuel mass flow to preburner
- {dot over (m)}SEV fuel mass flow to non-catalytic combustion chamber
- n rotor speed
- {circumflex over (n)} nominal rotor speed
- PACT actual effective power
- PSET set effective power
- P/{circumflex over (P)} relative power
- T1 temperature at inlet into catalytic combustion chamber
- T2 temperature at outlet of catalytic combustion chamber
- T3 temperature before turbine
- T4 temperature after turbine; waste gas temperature
- TMIN minimum required temperature at inlet into catalytic combustion chamber
- TMAX maximum permissible temperature at outlet of catalytic combustion chamber
- VIGV position of adjustable pre-guide row
- Y/Ŷ relative value
- YFUEL adjustment value for fuel mass flow
- YC adjustment value for fuel mass flow to catalytic burner stage
- YP adjustment value for fuel mass flow to preburner stage
- YSEV adjustment value for fuel mass flow to non-catalytic combustion chamber.
- YVIGV pre-guide row adjustment value
Claims
1. A method for operating a gas turbo group, which gas turbo group includes at least one combustion chamber, wherein the combustion chamber includes at least one catalytic, first burner stage and a second, non-catalytic burner stage following the at least one catalytic burner stage in the flow direction, the method comprising:
- supplying the gas turbo group with a total fuel mass stream ({dot over (m)}FUEL) of the gas turbo group;
- distributing the total fuel mass stream to at least the catalytic burner stage and the non-catalytic burner stage;
- determining the temperature (T2) at the outlet from the catalytic burner stage;
- regulating, limiting to a set value, limiting to a maximum value, or combinations thereof, the temperature at the outlet from the catalytic burner stage by changing the combustion air mass stream and blocking the fuel supply to the non-catalytic burner stage when the combustion air mass stream is below an achievable maximum;
- determining a net power output (PACT) of the gas turbo group; and
- regulating the fuel mass flow (mSEV) to the non-catalytic burner stage depending on a control deviation (PSET-PACT) of the net power output.
2. A method according to claim 1, wherein changing the combustion air mass stream comprises adjusting an adjustable guide row of a compressor of the gas turbo group.
3. A method according to claim 2, comprising:
- keeping the adjustable compressor guide row closed when the temperature at the outlet from the catalytic burner stage is below a set value.
4. A method according to claim 1, comprising:
- cooling suction air upstream from the compressor in order to increase the combustion air mass stream.
5. A method according to claim 4, further comprising:
- injecting fluid droplets into the suction air for cooling.
6. A method according to claim 1, further comprising:
- operating a non-catalytic preburner stage upstream from the catalytic burner stage.
7. A method according to claim 6, further comprising:
- determining the temperature (T1) at the inlet into the catalytic stage; and
- regulating compliance with a minimum value of the temperature at the inlet into the catalytic stage by adjusting the fuel mass stream {dot over (m)}p to the preburner stage.
8. A method according to claim 6, comprising:
- operating the preburner stage in a diffusion combustion mode.
9. A method according to claim 1, further comprising:
- in the presence of a maximum combustion air mass stream, supplying a fuel mass stream ({dot over (m)}SEV) additionally necessary for regulating the net power output to a combustion chamber or burner stage located downstream from the catalytic burner stage.
10. A method according to claim 1, further comprising:
- operating the second non-catalytic burner stage as a self-igniting combustion chamber.
11. A method according to claim 1, wherein the regulating value of the temperature at the outlet from the catalytic stage corresponds essentially to the maximum permissible temperature of the catalyst material.
12. A method according to claim 1, wherein the regulating value of the temperature at the outlet from the catalytic stage is higher than the temperature necessary for a spontaneous self-ignition of the fuel in the second non-catalytic burner stage.
13. A method according to claim 9, wherein the presence of a maximum combustion air mass stream comprises a fully opened adjustable guide row.
14. A method according to claim 9, wherein a combustion chamber or burner stage comprises the non-catalytic burner stage.
3975900 | August 24, 1976 | Pfefferle |
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20020056276 | May 16, 2002 | Dalla Betta et al. |
0 062 149 | October 1982 | EP |
0 321 809 | May 1991 | EP |
0 669 500 | August 1995 | EP |
0 694 740 | January 1996 | EP |
0 767 345 | April 1997 | EP |
- Search Report for CH 2003 1992/03 (May 13, 2003).
Type: Grant
Filed: Feb 11, 2004
Date of Patent: Jul 4, 2006
Patent Publication Number: 20040216462
Assignee: Alstom Technology Ltd. (Baden)
Inventors: Jaan Hellat (Baden-Ruetihof), Stefan Tschirren (Nunningen), Rolf Dittmann (Nussbaumen)
Primary Examiner: Louis J. Casaregola
Attorney: Cermak & Kenealy, LLP
Application Number: 10/775,141
International Classification: F02C 9/00 (20060101); F23R 3/40 (20060101);